A sterile device designed to seal the sheath of a haemostasis valve to maintain sheath patency (i.e., to prevent blood from coagulating in the sheath and blocking access through the haemostasis valve). It is typically a long, thin, rod-like device made of plastic with a rounded distal tip and a cap at the proximal end; it is available in a variety of sizes (e.g., 4-13 French and 15-26 cm long). The proximal cap has a locking mechanism (e.g., a Luer-lock or snap lock) to hold it securely in place to prevent blood loss from the patient. This is a single-use device.